Tech mogul Elon Musk has likened the Australian government to "fascists", attacking proposed laws that would fine social media giants for failing to stem the spread of misinformation.

Australia introduced a "combating misinformation" bill on Thursday, which includes sweeping powers to fine tech giants up to five percent of their yearly turnover for breaching online safety obligations.

"Fascists," posted Musk in a one-word reply on social platform X, formerly known as Twitter, which he owns.

Musk's salvo threatened to rekindle his long-running spat with the Australian government.

The country's online watchdog took Musk's company to court earlier this year, alleging it had failed to remove "extremely violent" videos that showed a Sydney preacher being stabbed.

But it abruptly dropped its attempt to force a global takedown order on X after Musk scored a legal victory in a preliminary hearing, a move he celebrated as a free speech triumph.

eSafety Commissioner Julie Inman Grant -- a former Twitter employee -- has said Musk's takeover coincided with a rise in "toxicity and hate" on the platform.

Musk has also been butting heads in Brazil, where a judge has effectively suspended X after it ignored a series of court directives.

Australia has been at the forefront of global efforts to regulate social media platforms.

Prime Minister Anthony Albanese unveiled plans earlier this week to ban children from social media until they are at least 14 years old.